Axial-flow blading with internal fluid passages



Aug. 28, 1962 D. A. ROBERTS ETAL 3,051,438

AXIAL-FLOW BLADING WITH INTERNAL FLUID PASSAGES Filed Feb. 12, 1958 a 33zatamw hi 3 2% f I? if 1%1 19 6 37%5 1% F .Z. 3 w

United States Patent Oflice 3,051,438 Patented Aug. 28, 1962 3,051,438AXIAL-FLOW BLADHNG WITH ENTERNAL FLUID PASSAGES Derek Aubrey Roberts,Breadsall, and Edward Page, Chellaston, Englam;i assikgnors toRolls-Royce Limited, Derb En land a ritis company ra a Feb. 12, 1958,Ser. No. 114,348 Claims priority, application Great Britain Feb. 22,1957 7 Claims. (Cl. 25339.15)

This invention comprises improvements in or relating to bladed rotor orstator constructions for axial-flow fluid machines, such for example ascompressors or turbines of gas turbine engines, and is concerned morespecifiically with such constructions in which a fluid is caused to flowthrough passages in the blades for heating or cooling purposes.

According to the present invention, a blade for use in bladedconstructions as above specified comprises internal bores extendinglengthwise of the blade and interconnected at their ends to afford asinuous flow path having an odd number of courses through which fluidflows in succession, there being an inlet to the one end of the path atone end of the blade and an outlet from the other end of the path at theopposite end of the blade. Each course may be afforded by a single boreor by a plurality of bores in parallel. Also, a blade may be providedwith a plurality of such sinuous flow paths, the paths having the sameor different odd number of courses and the paths being either completelyseparate or having one or more courses in common.

By adopting the invention, the bores may be made by acceptablemanufacturing methods giving bores of cornparatively largecross-sectional area while also obtaining a high ratio of the internalsurface area to the total cross-sectional flow area of a path soobtaining a good cooling efiiciency.

The inlet and the outlet of a sinuous flow path may have each a flowarea not less than and preferably substantially equal to the totalcross-sectional flow area of the path, and there may be provided a bleedhole of smaller flow area from the first course of the path at saidopposite end of the blade, so that a proportion of the fluid flowsthrough a single course of the sinuous flow path and the remainder flowsthrough the whole path. The bleed hole preferably has a flow area whichis considerably smaller than that of the inlet and outlet so that onlyaminor proportion of the fluid flows through a single course of thepath. The provision of such a bleed hole assists to prevent blocking ofthe flow path at the interconnection between the first and secondcourses by dirt or other matter entrained in the fluid. Furthermore,there may be provided a small area fluid inlet hole to a course orcourses other than the first course, for instance to the last course ofthe path so as to augment the flow in this course, and, by selecting theareas of the inlet hole and the bleed hole in relation to the areas ofthe inlet and outlet, the cooling or heating effect obtained and thecooling or heating efliciency may be adjusted having regard to thepressure difference in the fluid between the inlet and outlet.

One embodiment of this invention as applied to the cooling of turbinerotor blades will now be described with reference to the accompanyingdrawings in which:

FIGURE 1 is an axial section through part of a gas turbine, parts beingbroken away to show details of construction, and

FIGURE 2 is a view in the direction of arrow 2 on FIGURE 1.

The turbine illustrated comprises a casing 10 wherein the turbine rotor11 is rotatively mounted, a ring of nozzle guide vanes 12 extending fromthe casing 10 to inner stator structure 13 and guiding the hot workinggas to rotor blades 14 mounted at the periphery of the rotor 11, and anexhaust assembly which comprises a bullet 15 which defines with thedownstream portion of the casing 10 an annular exhaust passage for gasesleaving the turbine.

The blades 14 are shown as being mounted in the rotor by means of rootseach of which has a shoulder attachment portion 16 engaging acorrespondingly shouldered channel in the rotor discs, a platformportion 17 from which the blade extends and which together with theother platform portions forms an annular portion of the inner wall ofthe working gas passage of the turbine, and a stem 18 interconnectingthe attachment portion '16 and the platform portion 17.

The stems 18 are circumferentially narrower than the platforms 17 sothat tunnels 19 are formed between the stems. The blades are retainedagainst disengagement from the channels by tangs 20 on the attachmentportions 16, which tangs bear on one axial face of the rotor, and byplate means 21 which is retained against the opposite face of the rotorand engages by its outer edge in inwardly-facing channels 17a in theplatform 17. The plate means 21 may be annular and split along oneradius so as to be contractible and may be held in place on the rotor byhaving a flange 21a at its inner edge to occupy an inwardly facinggroove 11a on the rotor. The plate means 21 is in contact with thedownstream surfaces of the blade roots and of the rotor disc "11 andthus serves to blank off the downstream ends of the tunnels 19.

The blades 14 are also provided with integral tip shrouds 22 which runin a circumferential groove 23 in the casing 10 and which are formedwith radially projecting ribs 24 co-operating with the walls of thegroove 23 to form gas seals to prevent excessive flow of working gasaround the tips of the blades.

The blades 14 are also arranged to be cooled by passing through them acooling fluid, for example compressed air tapped from the compressor ofthe gas turbine. The air prior to being fed to the blades may be cooled,say by evaporation therein of a liquid, such as Water, sprayed therein.

Each blade 14 has within it bores forming a sinuous flow path comprisingthree courses 25, 26, 27 which extend through the length of the bladeand are connected in flow series. The first course 25' is in the form ofa drilling adjacent the mid-chord of the blade section and has an inlet30 thereto from a tunnel 19. The second course 26 is also a drilling ata position between the course 25 and the leading edge of the blade andis connected to the first course 25 at the tip of the blade by means ofa cross-passage 28. The outer ends of the courses 25, 26 are closed by aplate 31 let into the tip shroud 22 of the blade. The course 27 is afurther drilling, is adjacent the leading edge of the blade, and isconnected at the root end of the blade to course 26 by a cross drilling25 which is closed by a plug 32. The course 27 has an outlet 33 throughthe tip shroud 22 into the groove 23.

It will be seen that, in this instance, the areas of the inlet 30 andoutlet 33 are substantially equal to the flow crosssection of thesinuous path afforded by the three courses 25, 26, 27, and further thatthe path has a high ratio of surface area to flow cross-sectional areagiving a good cooling efficiency.

The compressed air for cooling is fed through a conduit 34 to the space35 between the rotor 11 and the stator structure 13, and then flowspartly into the working gas passage at 35 to prevent inward flow of thehot gas, and partly into the tunnels 19 and through the blades 14. Theair enters each blade through inlet 30 and then flows through courses25, 26, 27 in succession leaving the blade via outlet 33 into the groove23 whence it passes into the working gas passage.

In the construction shown, there is also provided a bleed hole 37 in theplate 31 at the end of the first course 25. The bleed hole 37 has anarea which is considerably smaller than that of the inlet 30 and itpermits a small proportion of the air flowing in course 25 to passdirectly into the groove 23. This arrangement prevents blocking of thecross-passage 28 by deposition of dirt or other matter, such as productsof a cooling liquid spray, entrained in the compressed air.

Also in the construction shown, there is provided an auxiliary inlethole 38 leading from the tunnel 19 directly to the inlet end of the lastcourse 27 of the flow path. The hole 38 has an area which isconsiderably smaller than the outlet 33 and it permits a smallproportion of the compressed air to flow directly from tunnel 19 intothe final course 27 of the sinuous flow path.

By selecting the sizes of the holes 37, 38 in relation to the flowcross-sectional area of the sinuous path, the proportion of air whichflows in a single course, to the proportion which flows through the:full length of the sinuous flow path, may be varied, so varying thecooling efiiciency and the cooling effect obtained for a given pressuredifference as between tunnel 19 and groove 23.

We claim:

1. A blade for use in a turbo-machine, which blade has an aerofoilsection, a leading edge and a trailing edge and has a plurality of boresextending lengthwise within it, the said bores being interconnected attheir ends to afford a sinuous flow path having an odd number of coursesthrough which fluid flows in succession, a first of said bores beingadjacent the said leading edge and a second of said bores being adjacentthe said trailing edge, a fluid inlet to the path opening into saidsecond of the said bores at its end adjacent one end of the blade and afluid outlet opening from the path leading from the first of said boresat its end adjacent the opposite end of the blade.

2. A blade according to claim 1, wherein each course comprises a singlelengthwise bore.

3. A bladed rotor for a gas-turbine Comprising a rotor disc, a ring ofaerofoil section blades, each blade having a leading edge and a trailingedge, each blade having at one end a root including a shoulderedattachment portion engaging a correspondingly shouldered channel in therotor disc, each of the blades further having an odd number of boresextending lengthwise therein from the root to adjacent its opposite end,a first of said bores being adjacent the said leading edge, a second ofsaid bores being adjacent the said trailing edge and a third of saidbores being between said first and second of said bores, the bores beinginterconnected adjacent the ends of the blade to form a sinuous flowpath having an odd number of courses through which fluid flows insuccession, a fluid inlet opening to said path opening into the end ofsaid second of the bores adjacent the said root and a fluid outletopening from the path leading from the end of said first of the boresadjacent the opposite end of the blade, and means connected to deliverfluid to the inlet openings of the flow paths in the blades, the fluidleaving the blades through the outlet openings adjacent the oppositeends of the blades.

4. A blade :for use in a turbo-machine, which blade has an aerofoilsection, a leading edge and a trailing edge and has a plurality of boresextending lengthwise within it, the said bores being interconnected attheir ends to afford a sinuous flow path having an odd number of coursesthrough which fluid flows in succession, a first of said bores beingadjacent the said leading edge and a second of said bores being adjacentthe said trailing edge, a fluid inlet to the path opening into saidsecond of the said bores at its end adjacent one end of the blade and afluid outlet opening from the path leading from the first of said boresat its end adjacent the opposite end of the blade, each coursecomprising a single lengthwise bore, the inlet and the outlet opening ofthe sinuous flow path each having a flow area substantially equal to thecross-sectional area of the bores, said first course of the path havinga bleed hole of smaller flow area at said opposite end of the blade, sothat a proportion of the fluid flows through a single course of thesinuous flow path and the remainder flows through the whole path.

5. A blade according to claim 4, wherein the bleed hole has a flow areawhich is considerably smaller than that of the inlet and outlet so thata minor proportion of the fluid flows through only a single course ofthe path.

6. A blade according to claim 4, comprising also a small area fluidinlet hole to one of said courses other than the first course.

7. A blade according to claim 4, comprising also a small area fluidinlet hole to the last course of the sinuous flow path.

References Cited in the file of this patent UNITED STATES PATENTS2,364,189 Buchi Dec. 5, 1944 2,603,453 Sollinger July 15, 1952 2,699,598Daugherty Jan. 18, 1955 2,778,601 Eckert M Jan. 22, 1957 2,883,151Dolida Apr. 21, 1959' 2,920,865 Lombard Jan. 12, 1960 2,945,671 PetrieJuly 19, 1960 FOREIGN PATENTS 292,537 Switzerland Nov. 2, 1953 1,130,996France Oct. 8, 1956

